The invention relates to improvements in vibration damping apparatus in general, and more particularly to improvements in apparatus for damping vibrations in power trains between the engines and variable-speed transmissions of motor vehicles. Still more particularly, the invention relates to improvements in vibration damping apparatus of the type wherein coaxial rotary flywheels can turn relative to each other against the opposition of one or more dampers.
It is known to connect a first flywheel of a composite flywheel in a vibration damping apparatus to the output shaft of an internal combustion engine, to connect a second flywheel of the composite flywheel with the input shaft of a variable-speed transmission which transmits torque to the wheels of the motor vehicle, to install a friction clutch between the second flywheel and the input shaft of the transmission, and to equip the damper or dampers with (a) one or more energy storing elements which are designed to store energy when the first flywheel is caused to turn relative to the second flywheel and/or vice versa, (b) with an input element, and (c) with an output element. One of the input and output elements is non-rotatably but axially movably coupled to one of the flywheels by means of a plug-in coupling which includes first profiles on the one element or on the one flywheel and second profiles provided on the one flywheel or on the one element and serving to transmit torque from the one flywheel to the one element or vice versa. Reference may be had to numerous United States and foreign patents and patent applications of the assignee of the present application.
An important advantage of a plug-in coupling in a vibration damping apparatus of the above outlined character is that it facilitates assembly and dismantling of the apparatus because each flywheel and the associated parts can be assembled into a discrete unit, and the two units are thereupon connected to each other by bringing the first profiles of the plug-in coupling into mesh with the second profiles. The two units are in requisite torque-transmitting engagement as soon as the first profiles are properly positioned with reference to the second profiles of the coupling.
In many types of vibration damping apparatus which are designed for use in power trains between the engines and variable-speed transmissions of motor vehicles and wherein two separately assembled units can be simply inserted into each other in order to establish a torque-transmitting connection by way of a so-called plug-in coupling, one or more parts frequently necessitate highly accurate mounting with a minimum of tolerances. For example, one or more parts of such apparatus must be received in channels or like spaces with a minimum of play in order to enhance the operation of the assembled operatus and/or to prolong the useful life of its parts. Ths holds especially true when a substantially flange-like radially disposed component must extend into an annular chamber which contains a supply of viscous liquid and the apparatus comprises means for expelling the confined liquid from one portion of the chamber into another portion when the two flywheels are caused to turn relative to each other. The quality of the viscous damping action depends to a great extent on the selection of flow restricting passages for the liquid, i.e., on the cross-sectional area of each clearance or gap for the flow of viscous liquid therethrough. The plug-in coupling ensures that the flange can actually float between the parts which flank the gap (in the axial direction of the apparatus), i.e., the flange can assume an optimum axial position for proper operation of the vibration damping apparatus. Proper operation is ensured if the flange does not bear against the parts which define the gap so that it does not jam or become clamped at a time when it should be free to turn with reference to the gap-defining parts. Thus, elimination or pronounced reduction of friction between the flange and the adjacent parts is a highly desirable feature of a properly assembled vibration damping apparatus.
A drawback of presently known vibration damping apparatus which embody plug-in type axial couplings of the above outlined character is that, due to unavoidable or necessary manufacturing tolerances, the profiles of the coupling are assembled with a certain amount of play which causes the generation of undesirable noise (known as chatter, rattling or clatter), especially during certain stages of operation of the engine and of the power train, for example, when the engine is idling, the clutch between the composite flywheel and the transmission is engaged and the transmission is not shifted into a forward or reverse gear.